A woman is killed in a locked room, and her daughter Susan confesses to the murder after apparently becoming possessed by the spirit of her long-dead younger brother. The Chief enlists a psychic to help him in his investigations, but the clues that she offers him seem to confuse more than they assist.

The Chief links his case with a psychiatrist, who turns out to be a psychopath with a passion for brainwashing. Before he can get his evidence together, however, Fran is taken as the next victim of the doctor's peculiar brand of therapy, and is programmed to kill Ironside. Meanwhile Susan has to face past guilt over the death of her brother before she can be safe from herself.

A British police inspector visits San Francisco for a conference, and whilst there assists his old friend Chief Ironside with an awkward investigation. It soon appears, however, that he knows more about the case than he should do, and that his involvement may have something to do with his deteriorating state of health.